Cathode contact layer design for preventing chromium contamination of solid oxide fuel cells

Abstract

In embodiments, a fuel cell stack is provided that includes an interconnect between a first fuel cell and a second fuel cell, and a contact layer in contact with, and disposed between, an electrode of the first fuel cell and the interconnect. The contact layer may include a chromium-getter material. This chromium-getter material may consist of lanthanum oxide, lanthanum carbonate, and/or calcium carbonate.

What is claimed is: 
     
       1. A fuel cell stack comprising:
 an interconnect disposed between a first fuel cell and a second fuel cell; and 
 a contact layer in contact with, and disposed between, an electrode of the first fuel cell and the interconnect, wherein the contact layer comprises:
 a porous electrically conductive material, and 
 a chromium-getter material disposed in pores of the porous electrically conductive material, the chromium-getter material being selected from the group consisting of:
 lanthanum oxide, 
 barium oxide, 
 lithium oxide, 
 sodium oxide, 
 an inorganic carbonate, nitrate, hydroxide, or acetate that reacts with chromium vapor in a range of 300 to 850° C. 
 
 
 
     
     
       2. The fuel cell stack of  claim 1 , wherein:
 the chromium-getter material is less than about 50% by volume of the contact layer. 
 
     
     
       3. The fuel cell stack of  claim 1 , wherein:
 the chromium-getter material is less than about 33% by volume of the contact layer. 
 
     
     
       4. The fuel cell stack of  claim 1 ,
 wherein the contact layer has an inorganic material volume defined as a volume of the contact layer minus a volume of the pores and minus a volume of any organic material in the contact layer; and 
 wherein the chromium-getter material comprises between about 15% and about 33% by volume of the inorganic material volume of the contact layer after heat treatment in a range of 600 to 850° C. 
 
     
     
       5. The fuel cell stack of  claim 1 ,
 wherein the contact layer has an inorganic material volume defined as a volume of the contact layer minus a volume of the pores and minus a volume of any organic material in the contact layer; and 
 wherein the chromium-getter material comprises between about 10% and 33% by volume of the inorganic material volume of the contact layer after heat treatment in a range of 600 to 850° C. 
 
     
     
       6. The fuel cell stack of  claim 1 ,
 wherein the contact layer has an inorganic material volume defined as a volume of the contact layer minus a volume of the pores and minus a volume of any organic material in the contact layer; and 
 wherein the chromium-getter material comprises between about 1% and about 50% by volume of the inorganic material volume of the contact layer after heat treatment in a range of 600 to 850° C. 
 
     
     
       7. The fuel cell stack of  claim 1 , wherein the contact layer comprises:
 at least two outer layers and a central layer, 
 wherein the central layer comprises the porous electrically conductive material and the chromium-getter material disposed in pores of the porous electrically conductive material, and 
 wherein the central layer has a porosity of between about 25% and about 70%. 
 
     
     
       8. The fuel cell stack of  claim 1 , wherein the contact layer comprises:
 at least two outer layers and a central layer, 
 wherein the central layer comprises the porous electrically conductive material and the chromium-getter material disposed in the pores of the porous electrically conductive material, and 
 wherein the central layer has a porosity of between about 30% and about 50%. 
 
     
     
       9. The fuel cell stack of  claim 8 , wherein:
 the central layer has a thickness of between about 10 μm and about 250 μm. 
 
     
     
       10. The fuel cell stack of  claim 1 , wherein:
 the chromium-getter material is about 20% by volume of the contact layer. 
 
     
     
       11. The fuel cell stack of  claim 1 , wherein the electrode is a cathode. 
     
     
       12. The fuel cell stack of  claim 1 , wherein:
 the contact layer has a thickness of between about 20 μm and about 525 μm. 
 
     
     
       13. The fuel cell stack of  claim 1 , wherein:
 the interconnect comprises a coating of manganese cobalt oxide spinel phases. 
 
     
     
       14. The fuel cell stack of  claim 1 , wherein the chromium-getter material is an inorganic carbonate selected from the group consisting of lanthanum carbonate, calcium carbonate, lithium carbonate, sodium carbonate, sodium hydrogen carbonate, and barium carbonate. 
     
     
       15. The fuel cell stack of  claim 1 ,
 wherein the contact layer includes:
 a first layer comprising a perovskite material, and 
 a second layer comprising the porous electrically conductive material and the chromium getter material disposed in the pores of the porous electrically conductive material. 
 
 
     
     
       16. A method of forming a chromium-getter contact layer in a fuel cell, the method comprising:
 applying a first layer to a fuel cell electrode or a fuel cell interconnect, wherein the first layer comprises a perovskite material; and 
 applying a second layer to the first layer, wherein the second layer comprises: 
 a porous electrically conductive material, and 
 a chromium-getter material disposed in pores of the porous electrically conductive material, the chromium-getter material being selected from the group consisting of:
 lanthanum oxide, 
 barium oxide, 
 lithium oxide, 
 sodium oxide, and 
 an inorganic carbonate, nitrate, hydroxide, or acetate that reacts with chromium vapor in a range of 300 to 850° C. 
 
 
     
     
       17. The method of forming a chromium-getter contact layer in a fuel cell of  claim 16 , wherein the chromium-getter material is an inorganic carbonate that comprises a cation and reacts with the chromium vapor to capture chromium atoms at an atomic percent ratio of cation to chromium of between about 1 and about 1.7 to 1. 
     
     
       18. The method of forming a chromium-getter contact layer in a fuel cell of  claim 16 , wherein the chromium-getter material is an inorganic carbonate comprises a cation and reacts with the chromium vapor to capture chromium atoms at an atomic percent ratio of cation to chromium of about 1 to 1.